IMs connecting to the internet...

[Slyke]

I know this is a very broad spectrum question...
But how do programs such as MSN, AIM, YIM, Myspace, ICQ and all those actually connect to the internet?

I never opened a port for them in my router but i do believe that they use the TCP protocol.

Do they somehow configure my router through a uPNP or what ever it's called?

The router's firewall should stop it shouldn't it?

Also, what could i search for to find the code for this answer... or what is the code for this answer... this is a problem that i always have when making programs that communicate over the internet.

In my router's Port Forwarding table, i noticed that there's a free UDP Port open, the port number is 161 and it's set to the broadcast address for the network that i'm on (which means it will allow any IP address on the network to recieve traffic through this port).

[sessi4ml]

Normally the ports are open to all users ...from the inside
and locked from the outside.
Users can get out, but not in.
Port forwarding is users entering from the outside and you want to direct them to a specific computer.
Example, Public address (100.100.100.100) can point to 192.168.1.42
This could be one port (port 80) or many or all.
I am running http://www.wfshome.com/ on one of my many computers
Did this help?

[Slyke]

I used to use that program!

Yes, that helped. Yeah, it's to allow external data to come in, that's what ports are for... but the problem is that when you recieve a message on say MSN, there has to be a port open for that. How does this happen?

[sessi4ml]

To receive a message, a few ways. You received a pop-up via port 80, or there is a program running and it has a port open.
https://www.grc.com/x/ne.dll?bh0bkyd2
This will check all ports, or click on ... "Common Ports"
If this answers your question, then close Thread, if not, I'm here.

[penagate]

http://en.wikipedia.org/wiki/Network_address_translation

[the182guy]

they dont have to port forward because your MSN/Yahoo/AIM client makes outgoing connections. Its as simple as that. You only port forward for incoming connections.

[Slyke]

So even though the connection is made out going... Data can still come in?

That means if i have a main server that accepts in comming connections that i can just make programs that make outgoing connections and they can recieve data off each other via this main server?

[RobDog888]

Moved

[sessi4ml]

So even though the connection is made out going... Data can still come in?

That means if i have a main server that accepts in comming connections that i can just make programs that make outgoing connections and they can recieve data off each other via this main server?

You are mixing ports opened for incomming data and ports opened for outgoing data.
Don't ! !
When you visit a web site, port 80 is open for out-going and returning ( this is how the packets of data are designed) Someone trying to gain access to your port 80...will not. And, the router might have these ports turned off...the server will not be able to access them...Did you try ...Check your Ports ?...my link

[Al42]

So even though the connection is made out going... Data can still come in?The only thing a NAT device prevents is the initial incoming connection - that has nothing to do with incoming data. Data can flow both ways on any connection, regardless of which end made the connection.

That means if i have a main server that accepts in comming connections that i can just make programs that make outgoing connections and they can recieve data off each other via this main server?That's how all the IM programs work. Every user makes an outgoing connection (for both outgoing and incoming data) to the server. If 'A' sends data to 'B', 'A's computer sends the data to the server, with 'B' marked as the recipient, and the server forwards the data to 'B's computer.

You just have to develop a protocol. How are the users designated? (Names? Numbers? IP addresses?) How is the initial message formed? Start of message? Recipient? Sender? End of message? Is the server going to wait for the end of message mark before sending it to the recipient, send each packet as received, receive and send every character? Is the recipient going to send back an acknowledgement? All that sort of stuff.